signal spreads from dendrites to cell body to axon hillock to axon terminals

exception:

Retinal Horizontal Cells
-sometimes have axons, sometimes not.
-even when present, axon does not conduct spikes but actually acts to keep two end of the cell isolated from one another
-both dendrites and axons receive and send signals

integral protein: alpha subunit does most of the work. Beta subunit helps the protein to fold

the affinity of the binding sites for Na and K change as enzyme is phosphorylated.

ATP phosphorylates
-puts a phosphate directly onto an amino acid on the cytoplasmic side of the protein
-drives a conformational change and changes the affinity
-change in ion affinity and change in conformation moves the ions across the membrane

E1 protein conformation has Na affinity

E2 has no Na affinity so they are dropped and move across. it has high K affinity so they bind

Driving Force

pumping of ions across the membrane produces differences in concentrations for ions

Na higher outside cell, K higher inside cell

this creates a potential for a concentration gradient because there is too much Na outside and K inside. Difference produces a voltage called the RESTING POTENTIAL.

Typical Volatage Gated Channel

K+ channel

Typical Ligand Gated Channel

acetylcholine receptor

Second Messenger Gated Channels

similar in structure to voltage gated channels

Unstimulated Resting Potential

-70 mV

opening and closing of channels produces a flow of ions into or out of cell

flow of ions makes a change in membrane potential

changes in membrane potential are responsible for communicating information from one cell to antoehr

The inside of the cell is more _______ (negative or positive) than the outside.